1. Field of the Invention
The present invention relates generally to a shut-off valve with a spherical plug, and more particularly to a shut-off valve assembly having a housing which defines a chamber and has at its two ends external threads. Retaining nuts for holding flange bushings are screwed onto the external threads. Sealing members are arranged on both sides of the spherical plug, wherein at least on one side the sealing member is mounted on a support element which is screwed into an internal thread of the housing. At least one flange bushing has sealing contact with the outer end of the support element facing away from the plug.
2. Description of the Prior Art
A shut-off valve of the above-described type is known from DE-C2-3044201. When the retaining nut is unscrewed in the valve of this type, turning of the flange bushing causes a screwed-in part to be simultaneously turned, particularly due to the great play of the thread, so that the sealing member is lifted from the spherical plug and the shut-off valve is no longer tight. This may be dangerous particularly when the shut-off valve is used with aggressive media. The shut-off valve is therefore only usable to a limited extent.
It is, therefore, the primary object of the present invention to provide a shut-off valve of the afore mentioned type which affords a tight sealing action even when a flange bushing at the outlet side is unscrewed and the connected pipe is loosened.
In accordance with another object of the invention, the sealing action of the spherical plug is to be self-tightening within a certain range in case of wear.